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I've also had my battery out to swap cells (using the threaded rods and jack approach) and while I did take a few pictures I was in too much of a hurry to fully document it or make notes at the time, so I don't now remember everything needed to write a full step by step description, but I can answer some questions if you get stuck.

Here's the pack being lowered down and raised up again:

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It weighs approx 200Kg so you'll need a low but sturdy trolley to support it and move it around.

Here's a few tips:

1) Don't forget to disconnect the connector for the fan in the battery pack as you lower the pack down - it's at the left hand rear corner of the pack and easy to miss. (I almost stretched the cable before I noticed it)

2) Be careful of the small brackets on the rear quarters of the pack that bridge across to the chassis - remove them before you start lowering the pack and make note of how they fit together. Mine were very rusty but still came apart.

3) Don't use a screwdriver to try to prise apart the high voltage connectors for the PTC heater or AC compressor at the front of the pack - the tabs break really easily as I discovered. (I broke the locking clip on one and had to use use a zip cable to keep them tightly pulled together on reassembly)

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4) It's critical to get the air input vent grommet properly re-engaged when you reinstall the battery pack. It's not possible to do this by just raising the pack up into place, you'll need to pull back the passenger footwell carpet and disconnect the vent tube that goes under the carpet from the front centre heater assembly to the grommet - which is located just in front of the high voltage disconnect port angled forwards towards the front of the car. My advice in hindsight would be to pull back the carpet and remove the vent tube before dropping the battery and having it exposed and ready as you bring the battery back up so that you can manipulate the gromit into engaging properly as the pack is raised the final amount.

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5) A lot of the retaining bolts for the plastic cover under the pack were rusted and snapped off for me (approx half of them) so have some 6mm bolts and a 6mm metric tap and appropriate drill bit on hand to drill out and retap any that break. This chore took a large chunk of the total pack reinstallation time for me... :(

6) There are a lot of bolts clamping down the plastic cover on top of the pack. They screw into a threaded insert not unlike the ones used in woodwork which screw into the plastic housing with a coarse thread. When you try to remove these bolts you may end up unscrewing the threaded inserts instead due to rust between the bolt and insert, and the insert is too big to come through the hole in the metal strip.

I ended up replacing all of these bolts as most of them were very rusty and difficult to remove and on a couple I had to drill them out of the inserts after I had removed the inserts... Look carefully at how the metal strips around the lid are connected - you can avoid unbolting most of the earth wires that go from the chassis to the metal strip - just leave the strips hanging attached to the earth wires - you'll possibly find them too rusty to unbolt anyway, as I did. To get a good water tight seal all the way around the lid you'll need to ensure that you salvage and reuse all the inserts if any come out.

7) Although you might be only removing the CMU boards, if you do need to remove any cells there are a number of plastic rivets that have to be cut to remove the plastic frame above the cells which aren't obvious. Here's a few pics of a cell module and an example of one of the rivets:

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8) Be extremely careful of the high voltages, obviously. Remove the high voltage safety link plug under the front left seat and disconnect the 12v battery before attempting to disconnect any orange cables or remove the pack. This will make it safe from the outside but not from the inside once you remove the top cover from the pack! Beware. The safety link plug is approximately half way along the series string which means there is still up to 180 volts DC available to shock you if you touch between different modules, so never do that. Be particularly careful about not touching anything in the middle busbar/fuse area while also touching a module as the ends of the strings are in that middle area where the orange cables enter the bottom.

A full length module of 8 cells is only 30v DC so you can't get a shock touching only within a module or from a module once removed from the pack, however you can still cause fire/heat etc if you accidentally short any cells with a spanner. Be really careful not to! Don't over tighten the nuts on the cells when refitting them as the mounting for the terminal plates that the studs are attached to can apparently be broken quite easily, and then you would need a replacement cell. Nipped with a small spanner is enough, this includes when you're putting a module back in the pack and reattaching its busbars.

9) If you're going to have the pack out for a long time (days/weeks) then I'd suggest to reconnect the 12v battery once the pack is out of the car. As long as you don't try to turn the key fully to READY mode the absence of the pack won't upset any of the ECU's and other functions like central locking will work. If you leave the 12v battery off for more than a month the BMU will apparently lose it's knowledge of the battery SoH which means a full battery calibration with a diagnostic tool will be required. So leave the 12v battery connected and then disconnect it again just before you refit the pack.

10) You will inevitably set an airbag fault code due to having the passenger seat and airbag removed - you'll need a diagnostic tool to clear the airbag fault code at the end.

11) Be really sure that you've identified the correct CMU board based on which cell voltage is faulting. See image in next post:
 

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Discussion Starter #24
G.a.r.y & DBMandrake - Thanks v much and as a small reward...

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At last! I'll try to do a full blog and upload it to my website in due course.

Who was it that has done a time-lapse video already?

Thanks again. MW
 

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Discussion Starter #26
Dunno... but it works...!...

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Blimey thats some dust !! Presumably with that age of vehicle it charged with a straight lead, i.e. no "brick" in the granny cable?

Cheers.
 

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Discussion Starter #28
"...i.e. no "brick" in the granny cable?" Correct.

Looks like a rat or a squirrel was living on top of the pack at some point (nuts shells and rat-sized poop). No obvious damage though... so far. I only lost 2 or 3 6mm bolts that hold on the plastic shield. Boy!, those M12 bolts holding the battery pack up were tight. Back 2 were a bit rusted in but you can get to the exposed ends (just) to give them some WD40.
 

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Discussion Starter #29 (Edited)
Battry opened... all CMU05 cells reading 4.1V so no defective cells, then... and all other Cell-blocks reading 32V, for that matter.

So cell-block 05 is out and (apparently defective) PCB removed...

IMG_2848.jpg
 

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Or will you replace the board and attempt a renumbering/programming procedure via MUT.
I think he said earlier he was going to try to renumber it ? It looks like he has a MUT-III so if it is possible to reprogram the boards then he may well be the first person to attempt this and confirm whether it is possible...

If it is successful that's a minor breakthrough because it would mean that providing you have the dealer diagnostic tool (MUT-III or Diagbox/Lexia 3 as applicable) then you could simply install any CMU board without having to worry about which position it came from or attempt elaborate and risky chip swaps. (Ether LTC or EEPROM)

Awaiting the results with interest. :)

One thing I would suggest to Martin to help verify whether renumbering really works (and that it's not just luck to get the right CMU board) is after installation first check all the individual cell voltages in MUT-III and/or Canion - if the CMU board is numbered wrong it will clash with another CMU, causing one bank of 8 cells to register invalid voltages, and a second bank may misread. (Two different banks will be broadcasting their cell voltages with the same source address - this may cause the figures to fluctute)

Then perform the action you think will renumber the cells and check all the voltages again. If there seems to be more than one procedure that might potentially renumber the cells, I would try them one at a time and recheck cell voltages in between so we can learn precisely which procedure triggers a renumber.

Assuming the battery replacement procedure has to be done to trigger a renumber be aware that the battery capacity calibration routine will need to be performed afterwards as the Ah capacity will be reset to the factory default of 45.8Ah. It would be interesting to see what your reported Ah capacity is before performing any procedures and also at the very end after the calibration process. They should be within about 2Ah of each other and initially after the calibration it may read slightly lower than before. (But this will change after some driving)

Good luck!
 

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I think he said earlier he was going to try to renumber it ? It looks like he has a MUT-III so if it is possible to reprogram the boards then he may well be the first person to attempt this and confirm whether it is possible...

If it is successful that's a minor breakthrough because it would mean that providing you have the dealer diagnostic tool (MUT-III or Diagbox/Lexia 3 as applicable) then you could simply install any CMU board without having to worry about which position it came from or attempt elaborate and risky chip swaps. (Ether LTC or EEPROM)

Awaiting the results with interest. :)

One thing I would suggest to Martin to help verify whether renumbering really works (and that it's not just luck to get the right CMU board) is after installation first check all the individual cell voltages in MUT-III and/or Canion - if the CMU board is numbered wrong it will clash with another CMU, causing one bank of 8 cells to register invalid voltages, and a second bank may misread. (Two different banks will be broadcasting their cell voltages with the same source address - this may cause the figures to fluctute)

Then perform the action you think will renumber the cells and check all the voltages again. If there seems to be more than one procedure that might potentially renumber the cells, I would try them one at a time and recheck cell voltages in between so we can learn precisely which procedure triggers a renumber.

Assuming the battery replacement procedure has to be done to trigger a renumber be aware that the battery capacity calibration routine will need to be performed afterwards as the Ah capacity will be reset to the factory default of 45.8Ah. It would be interesting to see what your reported Ah capacity is before performing any procedures and also at the very end after the calibration process. They should be within about 2Ah of each other and initially after the calibration it may read slightly lower than before. (But this will change after some driving)

Good luck!
Just to remind myself of all the excellent advice that Simon has provided, is to trial connect the battery, positioned sideways, via the data cables only and don't advance the key to ready.
 

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Just to remind myself of all the excellent advice that Simon has provided, is to trial connect the battery, positioned sideways, via the data cables only and don't advance the key to ready.
I can't claim credit for that one - that was one of Ruperts ideas... :)

Rupert turned the battery around and lifted it up a bit from the floor to reach it however as Martin has access to a hoist (so jealous!) it might be easier to just lower the car down over the battery until the battery is within a few inches of its normal position but not actually bolted in - and just connect the group of data cables on the left hand side, leaving all the high voltage cables disconnected and leaving the safety link plug removed.

Although you don't want to put the car into full READY mode (turning to the spring loaded start position) with the high voltage lines disconnected, it is OK to turn the key to the on position (battery gauge and dashboard lit up) as long as the data cables are connected, and in this condition it's possible to read the cell voltages from the pack (over canbus) even though the high voltage lines are disconnected.

This would allow the pack to be quickly removed again should the renumbering process fail and an alternative approach like a chip swap be needed.
 

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Discussion Starter #35
Hi All,

(Sorry, but I missed these last 3 posts before I continued tinkering...)

Well, progress... I think.

I have replaced the apparently failed main CMU05 PCB with my spare one and put it all back together, reintegrated CMU05 into the battery pack, detached some of the data cabling to allow it to drop down a bit...

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... lowered the car sufficiently to connect the 4 x signal connectors (only) to the battery...

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... (leaving the service plug disconnected), reconnected a fully charged 12V auxiliary battery under the bonnet, connected the MUT3 and fired up the Windows XP laptop runing the MUT3 software.

This is what the dash looked like at ignition on (first position only)...

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Note the empty fuel gauge (charge symbol in the middle is flashing).

MUT3 app showing first page of diagnosis…

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WIth 'BMU' highlighted on the left, click the tick and we get...

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Click on special Function' option (wish I had looked at the 'Self Diagosis' first at this point) and we get ...

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… and note the option ‘CMU ID Numbering’ which when pressed gives…

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Click on the 'tick' (= 'OK') and when ‘Complete' (only a few seconds), go back to the previous screen...

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...and select ‘Self Diagnosis’…

(cont...)
 

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Discussion Starter #36
This gives (2 pics to show full list of DTCs)...
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A few new DTCs have appeared (and no sign of the old ones) but when cleared using ‘Erase DTCs’…

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No idea what U1937 is but probably relates to the 2nd PCB that the one I replaced was plugged into still being the original one? The P1A9F code I assume is the system recording that CMU05 was renamed (but not what it was before).

Going back to the beginning screen and highlighting 'CMU' instead of 'BMU' and doing a 'self Diagnosis' on CMU5 shows...

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… and at some point along the way the dash has changed to…

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Back in the BMU, deleting all DTCs again gives …

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Now disconnecting the MUT3 and trying Canion shows…

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And no weird behaviour any more.

So, the first question now is, should I replace cell 42 whilst I have the pack off and have a spare to hand? It’s only 0.15V away from the highest other cell…

Next question is the battery capacity measuring proceedure... You can see from the BMU Special Function screen (way above) there are 2 options 'Ready' and 'Action'. I'm wondering if these are the same as the Diagbox's 2 stages to do the same thing? If I remember right from another thread, there is a preperation stage and then the actual test. I will, of course have to reconnect at least the right side HV cables and the Service Plug but also the other HV cables? Probably not.

To answer DBMandrake (Simon)'s question, I'm pretty sure I noted from one of the MUT3's screens (above but not photographed) that the system was reporting the battery at ~37Ah but I'll check tomorrow before I try anything else.

Anything else to consider before I proceed (tomorrow)?
 

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Discussion Starter #37
Aside from anything else, it is interesting to note that there appears to have been very little discharge of the pack over the 18 months or more it has been sitting un-charged and un-driven most of which has been without a 12V auxiliary battery too.
 

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Wow, great success - it looks like you have confirmed that it is possible to renumber CMU boards - at least on the i-Miev using MUT-III. Excellent. :)

The Ion and C-Zero of course have to use Diagbox/Lexia 3, and I don't recall seeing a "CMU cell numbering" special function in the BMU in Diagbox. I might hook mine up over the weekend to have a poke around to see if I can find it as the wording is probably quite different. (And poorly translated from French!)

If renumbering is not available as a discrete function on Diagbox it might still be possible to do the renumbering by performing the battery swap procedure, but we would have no way of knowing unless someone with a misnumbered CMU tried it...
A few new DTCs have appeared (and no sign of the old ones) but when cleared using ‘Erase DTCs’…

View attachment 130603

No idea what U1937 is but probably relates to the 2nd PCB that the one I replaced was plugged into still being the original one? The P1A9F code I assume is the system recording that CMU05 was renamed (but not what it was before).
I can't find any mention of P1A9F for the i-Miev however I did find that fault code for the Outlander and it looks like it applies:


Since it disappeared later when you cleared the codes again it must have been set when you initially connected the repaired module back into the pack, but before renumbering it. Given the description of the fault code I think this is fairly solid evidence that there was an ID clash initially, but that the clash was resolved after the renumbering.

Now disconnecting the MUT3 and trying Canion shows…

View attachment 130608

And no weird behaviour any more.

So, the first question now is, should I replace cell 42 whilst I have the pack off and have a spare to hand? It’s only 0.15V away from the highest other cell…
This a tough call to make as you only really have one snapshot - cell voltages at an approximate 77% SoC.

I say approximate, because if the car was left sitting for 6+ months without use and the 12v battery was left disconnected the traction battery would have self discharged significantly (maybe 20% ish) but the BMU wouldn't be aware of the passage of time to account for self discharge as it wasn't powered up.

When it's powered up again after so long (and especially after the CMU fault) it will try to estimate the SoC using voltage estimation but this is quite inaccurate between about 20-80% SoC, so it says 77% SoC but there is likely to be quite an error.

Also if the cell voltages were continuously high for 6 months there may have been significant cell degradation which the BMU also won't be aware of since it was powered down. In short, until you charge the battery right up the SoC won't be correct, and until it's had a few full cycles (or put through the battery capacity calibration) it won't have an accurate Ah/SoH figure either.

Anyway given that you only know the voltage is 55mV down at 77% you can't be sure whether the cell is weak or whether it is just out of balance due to someone previously swapping it or a problem with the battery management system not keeping the cell in balance - although cell 42 is in a different module to 38 (the one the LTC chip was giving false low voltage warnings for) so it seems unlikely that you would have a faulty LTC chip in two different modules, since the LTC chip handles both voltage measurement and cell balancing.

So I'd say it's more likely the cell is weak than just out of balance, and that replacing the cell is probably a good idea, however there are two cavets/gotcha's:

1) You want to be sure that the Ah capacity of the replacement cell (presumably second hand) is at least as good as the weakest other cell in the pack, preferably better, otherwise you could conceivably end up reducing the usable capacity of the pack if the original cell was in fact just out of balance and not faulty.

However you don't know what the usable capacity of the rest of the pack without charging it up and running a calibration, so you don't know how good your replacement cell needs to be. And of course you need a way to measure the capacity of the stand alone cell.

When I did my cell swaps I tested my second hand cells before fitting using a hobby RC charger which has a Lithium Ion charge/discharge mode. The car doesn't use the cells over the full 4.1v to 3.0 volt range that most discharge tests use, it only goes down to approx 3.6 volts. When I tested my replacement cells they measured about 40Ah down to 3.6 volts and 43Ah if I went down to 3.0 volts, so usable capacity in the car should be about 40Ah - better than any of the other cells in the pack at the time.

2) It's absolutely critical to balance the replacement cell SoC (referenced to 100% SoC!) to match the pack before you fit it, and doing this at anything other than 100% SoC (4.1 volts) is a bit of guesswork if you don't know the exact capacity of the cells.

I made the mistake of doing my cell swap at 30% SoC - I externally charged the replacement cells to the average voltage of the other cells within about 30mV however I didn't take into account the fact the replacement cells had considerably more capacity than any of the old ones, so of course as they charged up the old cells reached full charge (4.1v) first with the new cells lagging behind almost 50mV by the time charging was completed, leaving the pack significantly out of balance.

A 50mV imbalance at full charge doesn't sound like much but works out to approximately 2Ah of charging left to do on the replacement cells. 2Ah doesn't sound like much but the balance bleed resistors in the CMU boards only draw 100mA when switched on, which means it would take 20 hours of bleeding all the high cells to bring them into balance with the new cell.

However the BMU will only perform balancing in the last hour or two of charging, and the balance resistors can't run at 100% duty cycle due to thermal limits (they're tiny surface mount resistor groups on the PCB) so it takes a long, LONG time to even balance out a 50mV / 2Ah error. I was driving 40 miles a day and charging every night at the time I did the cell swap and it took nearly 2 months of cycling the battery daily for the self balancing system to finally finish balancing the cells. :( (It did get there in the end though)

If the imbalance is too great >50% SoC the BMU will also set a fault code and refuse to charge - although my imbalance wasn't enough to trigger this thankfully.

If I was to do my cell swap again knowing what I do now I'd do it at 100% SoC - charge the car up until it stops charging, this should bring all the good cells up to 4.1 volts - don't worry about the bad cell which will be lower - it will try for a few hours to balance it then give up.

Charge the replacement cell externally to precisely 4.1 volts using a safe Lithium Ion charger such as a Hobby RC charger before fitting, that way the balance will be perfect and the pack will be at 100% SoC once the swap is done, ready to do a calibration. It does of course mean connecting up the pack to the car twice...

Or you can just try to charge/discharge the replacement cell to the same voltage as the cells in the pack and take your chances fitting it. At 77% SoC (supposed) any errors due to differences in cell capacity will be greatly reduced compared to when I did it at 30%, (since the voltage slope is much steeper at a low SoC) however you're unlikely to get a perfect balance on first charge and it may still take many cycles to finish balancing.

If there is a significant SoC imbalance between new and old cells it will affect the capacity measurement as not all the capacity will be usable depending on the relative capacity of the cells and degree of imbalance. So you might need to do a second calibration after the imbalance is finally ironed out.

The balancing system works well on these cars so it should eventually reach a balance of +/-5mV between all cells.
Next question is the battery capacity measuring proceedure... You can see from the BMU Special Function screen (way above) there are 2 options 'Ready' and 'Action'. I'm wondering if these are the same as the Diagbox's 2 stages to do the same thing? If I remember right from another thread, there is a preperation stage and then the actual test. I will, of course have to reconnect at least the right side HV cables and the Service Plug but also the other HV cables? Probably not.
You will definitely need HV cables connected to do the battery calibration. As to how you initiate it on MUT-III I don't know sorry. The procedure actually differs between different versions of Diagbox let alone between Diagbox and MUT-III.

On Diagbox you go through multiple steps, the first one tells you to run the heater until the lowest cell drops to around 3.75v, then you move onto the next step where you plug the car in and let it charge to 100%, then the final step writes the new Ah value into the BMU. At least that's how my version of Diagbox does it.
 

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Discussion Starter #40
Simon et al,

Thanks v much for the input, most encouraging I agree.

Any thoughts about the 'BAT-LIN Slave Error'? I can't find any reference to it on the web or the service manual.

Just one point before I move on... I originally owned an iOn which is why I bought my Chinese clone MUT3 (for about £300 IIRC) and it worked fine on it... just the same as on this i-MiEV. I don't know what the Diagbox costs as I have not had any thing to do with one...

I think it would be worth conncting the pack HV leads; inverter/AC charger, A/C pump and heater as the latter 2 are (I gather) used for the battery capacity measurement procedure, but not CHAdeMO port.

At thispoint I'll see if the car goes to 'Ready' and/or if it will charge (just enough to see if it works) as without those I won't have made any progress, really.

If they work OK, I'll then have a look at the 'Battery Maintenance Function' to see what's in there (I think I did before what it did not look interesting/helpful so I ignored it). I'll then try the battery capacity measuring proceedure, 'Ready' and then 'Action' and repoert back.
 
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